<!DOCTYPE html>
<html>

<head>
  <script src="https://cdn.staticfile.org/jquery/1.10.2/jquery.min.js"></script>
  
  <title>you are pig</title>
</head>

<body>
  <h2>Head in javascript</h2>
  <a href="https://zhuanlan.zhihu.com/p/54510444" target="_blank">Fuck A* <br /></a>

  <button id="button_1">print number</button>
  <button id="button_2">print date</button>
  <button id="button_3">hide</button>
  <button id="button_4">show</button>

  <p id="demo">TEST <br /></p>

  <script>
    $(document).ready(function () {
      $("#button_3").click(function () {
        $("p").hide();
      });
    });

    // this kind of code has the same effect.
    // which is more simple
    ///
    $(function () {
      $("#button_4").click(function () {
        $("#demo").show();
      })
    });


  </script>



<script src="stl.js"></script>
</body>

</html>